MEPS 169:237-242 (1998)  -  doi:10.3354/meps169237

ABSTRACT: Two naturally occurring dinoflagellates, the autotrophic Prorocentrum micans and the heterotrophic Noctiluca scintillans (non-bioluminescent), and the green alga Dunaliella tertiolecta were tested as prey for the first zoeal stage of the brachyuran crab Cancer magister under controlled laboratory conditions. Each dinoflagellate was tested alone and in combination with a suboptimal application of the nauplius of the brine shrimp Artemia sp., a diet of known value. When offered alone, both dinoflagellates delayed mortality as compared to an unfed control, but neither supported development to the second zoeal stage. When larvae were fed a cycle of 1 d of Artemia sp. nauplii, followed by 2 d of either dinoflagellate, survival to zoeal stage II was significantly higher than for larvae fed 1 d of nauplii followed by 2 d unfed. Indeed, survival was equal to a control that had been fed nauplii continuously, although there was a significant delay in time to molt. Larvae fed D. tertiolecta in combination with nauplii showed a reduction in survival as compared to the suboptimal nauplius diet alone and no difference in time to molt. All 3 protists were consumed and the 2 dinoflagellates contributed nutritionally. Given the susceptibility of newly hatched brachyuran larvae to starvation, their ability to prey upon protists may be significant, especially for C. magister, a species that hatches in the Puget Sound (WA, USA) region in winter, a time of very low primary productivity. Crab larvae that can consume protistan prey may serve as a link between the rich carbon sources of the microbial food web and metazoans.

KEY WORDS: Crab larvae · Nutrition · Protists · Dinoflagellates